Objective: We propose to develop nanomechanical sensors for ultrasensitive detection of breast cancer biomarkers such as CA27.29 and CA15.3. Our approach to diagnosis and prognosis of breast cancer biomarkers is fundamentally important, as high sensitivity will enable early detection of breast cancer, as well as monitor disease progression or therapy with a resolution of 1-10 U/microliter, roughly 10-100 times more sensitive than current detection techniques, including chemiluminescent assay. We expect the nanosensors to provide superior sensitivity to that of histochemical assays, and to approach the sensitivity of the best available fluorescence assays. We propose to investigate the feasibility of incorporating multiple sensors on one chip, laying the foundation for later studies that may lead to a high-throughput, sensitive, parallel biosensor chip for breast cancer based on nanotechnology methods. Towards a focused effort, we propose to demonstrate ultrasensitive detection of CA27.29 with our nanomechanical sensor. Specific Aims: 1) Design and simulation of cantilever-based mechanical biosensor; 2) Nanoabrication and surface biofunctionalization with antibody; 3) Detection of CA27.29 by biofunctionalized nanomechanical sensor; 4) Detection of CA27.29 with 1-10 (Unit/microliter) sensitivity by biofunctionalized nanomechanical sensor. Relevance to public health: It is becoming increasingly evident that breast cancer is a disease in which each patient's tumor may be unique, requiring treatment protocols that are tailored to the individual. There is a need for developing tools that can rapidly classify the individual patient's disease according to its molecular "fingerprint", which may consist of detecting the presence of hundreds of biomarkers or genes. Such a tool must also be relatively inexpensive. The semiconductor industry has long demonstrated how miniaturization can result in cost reduction without sacrificing capability. This application is to adapt some of the techniques of semiconductor processing to developing nanosensor probe arrays for breast cancer biomarkers. [unreadable] [unreadable] [unreadable]